Fuel injection pumps



Jan? 5, 1960 w. FRIEDLANDER 2,919,687

FUEL INJECTION PUMPS Filed July 5, 1957 \NVENTOR Wm M, M w WM ATTORNEYS,

FUEL INJECTION PUMPS William Friedlander, London, England, assignor toMono- Cam Limited, London, England, a British company Application July5, 1957, Serial No. 67il,1ll5

Claims priority, application Great Britain .luly 10, 1956 11 Claims.(Cl. 123-139) The invention relates to fuel injection pumps for internalcombustion engines, e.g. diesel engines or other compression-ignitionengines.

The invention provides, in one of its aspects, a fuel injection pump foran internal combustion engine, which pump comprises one or more pumpingelements, means adapted to be driven by the engine for operating thepumping element (or each pumping element in turn) to supply fuel to anoutlet for each injection period, means for causing the pumping elementto supply fuel to a spill chamber at the end of each injection period soas to provide in the spill chamber a pressure which increases withincrease in the engine speed, and means actuated or controlled by thatpressure to advance the timing of the injection periods in relation tothe operation of the engine as the said pressure increases.

Preferably the means for operating the pumping element or elementsinclude a rotatable drive having two parts, and the said means foradvancing the timing comprise a helical connection between the said twoparts, means biassing the two partsaxially to assume one relativeangular relationship and means for applying the said pressure inopposition to the biasing means so that the relative angularrelationship between the said two parts varies with the said pressure. A

A specific construction of a fuel injection pump em bodying theinvention will now be described by way of example and with reference tothe accompanying drawing, which is a longitudinal sectional view of thepump. 7 In this example the pump comprises a plurality (e.g. four orsix) pumping elements arranged in a circle each of which elementscomprises a piston 11 working in a cylinder 12 having inlet ports 13 andan outlet 14. The

piston is urged to the limit of its suction stroke by a helicalcompression spring 15 which bears at one end on a washer 16 engaging ahead 17 on the piston and bears at its other end on a fixed abutment 18.The head 17 bears in turn against a shoe 19 carrying a roller 21rotatable on a pin 22 and in contact with a cam 23. The cam 23 is formedintegrally with a hollow shaft 24 which fits over a shaft 25 and ismounted in bearings 26, 27. The shafts 24, 25 are drivingly connected byhelical splines 28. The cam shaft 24 is held against axial movement butthe shaft 25 is axially movable and is provided with straight splines 29to permit it to be driven from the engine while permitting axialmovement of the shaft 25. The shaft 25 is urged inwardly of the pump bya helical compression biassing spring 31 which acts between a fixedshoulder 32 and a head 33 on the shaft. That head 33 abuts, through aball bearing 34, against the inner face of a non-rotating piston 35working in a cylinder 36. The cylinder 36 communicates through a passage37 with a spill chamber 38.

Each piston 11 is provided with an annular spill port 41 which isconnected by a passage extending axially through the interior of thepiston 11 with the working face 42 thereof. During each pressure strokeof the piston 11 the spill port 41 is covered by a controlling atent O"ice sleeve 43 until the end of the injection period, which isterminated by the spill port 41 emerging from the sleeve 43 so that thefuel is then supplied to the spill chamber instead of to the outlet 14.

The controlling sleeves 43 of all of the pumping elements are carried bya member 44 and are movable therewith all in unison. The member 44 isurged by the fuel pressure in the spill chamber against the action of ahelical compression governor spring 45 which acts between a stop 46provided on a control pin 47 and an inturned rim 48 on the member 44.The split fuel is returned to the feed circuit 49 of the pump, which isat a lower pressure, through a passage 51 and an aperture 52 formedbetween the interior of the member 18 and a tapered portion of the pin47. The governed speed of the engine is determined by the position ofthe pin 47, which is adjustable by a lever 53, and that speed isincreased by moving the pin 47 to compress the governor spring 45. Thisprovides a spill pressure characteristic which increases with enginespeed.

The spill pressure acting as aforesaid on the piston 35 causes it tomove until a state of equilibrium is reached between the spill pressureforce acting on the piston 35 and the spring 31 acting thereon. Movementof the piston 35 causes corresponding axial movement of the shaft 25,with a consequent change in the relative angular relationship betweenthe cam shaft 24 and the shaft 25, due to the helical splines 28. Thecam 23 is thus correspondingly moved angularly with respect to the drivefrom the engine and the timing of the injection is thus advanced withrise in engine speed and is retarded again when the engine speed falls.

The invention is not restricted to the details of the foregoing example.

T he pressure in the spill chamber varies also with the engine load inthe foregoing example, so that the timing of the injection periods maybecome more advanced than may be considered desirable with relativelyhigh engine speeds and relatively light loads. The travel of the piston35 may be limited so that the automatic advance of the injection periodsis effective only up to a selected speed, above which no further advancetakes place.

The invention may be applied'to other kinds of fuel injection pumps forinternal combustion engines eg, it may be applied to such pumps havingtheir pumping elements arranged in-line.

I claim:

l. A fuel injection pump for an internal combustion engine, comprisingin combination at least one pumping element, rotary cam means rotatableto operate said pumping element to supply fuel to an outlet forinjection periods, means preventing axial movement of said cam means,coupling means for driving attachment to an internal combustion engineand to be driven thereby, a helical driving connection between saidrotary cam means and said coupling means, said pumping element beingreciprocable in a direction parallel to the axis of rotationof saidhelical driving connection, a spill chamber, means for supplying fuel tosaid spill chamber at the end of each injection period whereby fuelpressure in said spill chamber increases with increase in engine speed,and means responsive to said fuel pressure for advancing the timing ofthe ignition periods in relation to the operation of the engine as saidfuel pressure increases. v

2. A fuel injection pump for an internal combustion engine, comprisingin combination at least one pumping element, rotary cam means rotatableto operate said pumping element to supply fuel to an outlet forinjection periods, means preventing axial movement of said cam 1 means,coupling means for driving attachment to an v.3 internal combustionengine and to be driven thereby, a helical driving connection betweensaid rotary cam means and said coupling means, said pumping elementbeing reciprocable in a direction parallel to the axis of rotation ofthe said helical driving connection, a spill chamber, means forsupplying fuel to said spill chamber at the end of each injectionperiod, and means responsive to fuel pressure in the said spill chamberfor advancing the timing of the injection periods.

3. A fuel injection pump for an internal combustion engine, comprisingin combination a plurality of pumping elements distributed around apitch circle, a single annular rotary cam rotatable to operate the saidpumping elements in turn to supply fuel to a plurality of outlets inturn for jection periods, means preventing axial movement of said cam,coupling means for driving attachment to internal combustion engine andto be driven thereby, a helical driving connection between said rotarycam and said coupling means, said rotary cam and said pitch circle beingco-axial with said helical driving connec ion, a spill chamber, meansfor supplying fuel to said s ill chamber at the end of each injectionperiod whereby fuel pressure in said spill chamber increases withincrease engine speed, and means re sponsive to said fuel pressure foradvancing the timing of the injection periods in relation to theoperation of the engine as said fuel pressure increases.

4. A fuel injection pump for an internal combustion engine, comprisingin combination at least one pumping element, relatively rotatable camand cam follower means to operate said pumping element to supply fuel toan outlet for injection periods, means preventing axial movement of saidcam, coupling means for driving attachment to an internal combustionengine and to be driven thereby, a helical driving connection betweensaid relatively rotatable cam and cam follower means and said couplingmeans, said pumping element being reciprocable in a direction parallelto the axis of rotation of the said helical driving connection, a spillchamber, means for supplying fuel to said spill chamber at the end ofeach injection period whereby fuel pressure in said spill chamberincreases with increase in engine speed, and means responsive to saidfuel pressure for advancing the timing of the injection periods inrelation to the operation of the engine as said fuel pressure increases.

5. A fuel injection pump for an internal combustion engine, comprisingin combination a plurality of pumping elements distributed around apitch circle, relatively rotatable cam and cam follower means to operatesaid pumping elements in turn to supply fuel to a plurality of outletsin turn for injection periods, coupling means for driving attachment toan internal combustion engine and to be driven thereby, means preventingaxial move ment of said cam, a helical driving connection between saidrelatively rotatable cam and cam follower means and said coupling means,said relatively rotatable cam and cam follower means and said pitchcircle being co-axial with said helical driving connection, a spillchamber, means for supplying fuel to said spill chamber at the end ofeach injection period, whereby fuel pressure in said spill chamberincreases with increase in engine speed, and means responsive to saidfuel pressure for advancing the timing of the injection periods inrelation to the operation of the engine as said fuel pressure increases.

6. A fuel injection pump for an internal combustion engine, comprisingin combination at least one pumping element, relatively rotatable camand cam follower means to operate said pumping element to supply fuel toan outlet for injection periods, the operative face of said cam beingtransverse to the axis of rotation of the cam, means preventing axialmovement of said cam, coupling means for driving attachment to aninternal combustion engine and to be driven thereby, a helical drivingconnection between said relatively rotatable cam and cam follower meansand said coupling means, said pumping element being reciprocable in adirection parallel to the axis of rotation of the said helical drivingconnection, a spill chamber, means for supplying fuel to said spillchamber at the end of each injection period whereby fuel pressure insaid spill chamber increases with increase in en ine speed, and meansresponsive to said fuel pressure for advancing the timing of theinjection periods.

7. A fuel injection pump for an internal combustion engine, comprisingin combination at least one pumping element, a single annular rotatablecam having a cylindrical bore, means preventing axial movement of saidcam, helical threads formed on the surface of the said cylindrical bore,a cylindrical driving shaft rotatable within the said bore,corresponding helical threads formed on the surface of the said shaftand meshing with the said helical threads on the surface of thecylindrical bore, longitudinal splines formed on the surface of the saidshaft for engagement with corresponding parts in an internal combustionengine, and at least one cam follower means to operate the said pumpingelement, a spill chamber, means for supplying fuel to said spill chamberat the end of each injection period, whereby fuel pressure in said spillchamber increases with increase in engine speed, and means, responsiveto said fuel pressure, whereby said driving shaft is moved axiallyrelatively to said cam to advance the timing of the injection periods inrelation to the operation of the engine as said fuel press areincreases.

8. A fuel injection pump for an internal combustion engine, comprisingin combination at least one pumping element, a single annular rotary camrotatable to operate said pumping element to supply fuel to an outletfor injection periods, means preventing axial movement of said cam,coupling means for attachment to an internal combustion engine and to bedriven thereby, a helical driving connection between said rotary cam andsaid coupling means, said rotary cam being coaxial with said helicaldriving connection, a spill chamber, means for supplying fuel to saidspill chamber at the end of each injection period, whereby fuel pressurein said spill chamber increases with increase in engine speed, and meansresponsive to said fuel pressure for advancing the timing of theinjection periods in relation to the operation of the engine as saidfuel pressure increases.

9. A fuel injection pump for an internal combustion engine, comprisingin combination at least one pumping element, a spill chamber, means forsupplying fuel to said spill chamber at the end of each injection periodwhereby fuel pressure in said spill chamber increases with increase inengine speed, a rotary cam having an axis of rotation parallel to thedirection of reciprocation of the pumping element to operate the saidpumping element to supply fuel to an outlet during an injection periodand having an operative face transverse to the axis of rotation of thecam and provided with an axial cylindrical bore formed with helicalthreads on the surface of the bore, means preventing axial movement ofsaid cam, a cylindrical driving shaft rotatable within said bore,helical threads formed on the shaft and meshing with said helicalthreads on the surface of the bore of the cam, longitudinal splinesformed on the shaft for engagement with corresponding parts in aninternal combustion engine, at least one cam follower means to operatethe said pumping element, a cylinder communicating with said spill.chamber, a cylindrical piston in said cylinder and eyond one end of thesaid shaft, whereby as the said fuel pressure increases said pistonmoves in response thereto and is constrained by the cylinder to bearagainst the one end of the driving shaft and push it relatively to saidcam to advance the timing of the beginning and the end of each injectionperiod in relation to the operation of the engine.

ii). A fuel injection pump as claimed in claim 9, in which a pluralityof pumping elements are arranged around a pitch circle co-axial with thesaid axis of rotation of the cam.

11. A fuel injection pump as claimed in claim 9, in which the said meansfor supplying fuel to said spill chamber at the end of each injectionperiod comprise a member reciprocable in said spill chamber andco-operating with each pumping element, the position of said member insaid spill chamber being determined by said fuel pressure in said spillchamber, whereby the said 6 timing of the end of each injection periodis detrrriineci by the combination of the angular position of said camwith respect to the said driving shaft and the position of said memberin said spill chamber, and the timing of the beginning of each injectionperiod is independent of the position of said member in said spillchamber.

References Cited in the file of this patent UNITED STATES PATENTS FOdOlMar. 5, 1946

